Rapid fluid mixer

ABSTRACT

A mixer and method of mixing are described which involves forming a viscous first fluid into a thin film by passage through an annulus and then injecting a second fluid into the flowing liquid. Injection may be through either annulus-forming surface or both in various patterns. A particular mixer adapted for use in the uniform mixing of rennet and precheese. The precheese is suitably formed by ultrafiltration of milk. The mixer forms an annulus and injects rennet circumferentially into the surface of precheese/retentate flowing in the form of a thin film through the annulus formed by the mixer. Downstream of injection, additional mixing means may be included to further enhance mixing. The mixer is adapted for modification and facile disassembly for cleaning to maintain sanitary standards.

This application is a divisional of application Ser. No. 08/694,229filed Aug. 8, 1996, now U.S. Pat. No. 5,753,282, granted May 19, 1998,and also claims the benefit of U.S. Provisional Application No.60/002,155, filed Aug. 11, 1995.

FIELD OF THE INVENTION

The invention relates generally to mixers for fluids and specifically amethod and apparatus for mixing a coagulant such as rennet andprecheese.

BACKGROUND OF THE INVENTION

The prior art has used both batch mixing and conduits with interiorvanes/baffles to effect mixing. In the preparation of admixtures ofcoagulant and precheese, such procedures, using conventional mixingdevices, often produce uneven mixing and, as a consequence, irregularcoagulation occurs.

SUMMARY OF THE INVENTION

The mixer of the present invention is designed to effect rapid uniformmixture of two fluids and is most useful where its attributes areessential, that is, where the combination of fluids interacts or reactsand the product is non-uniform or otherwise detrimentally affected whereproduction of a uniform mixture occurs over time. The advantage of rapidand uniform mixture, in accordance with the present invention, ismagnified where (1) at least one of the fluids is a liquid of highviscosity and (2) the viscous liquid is mixed with a second fluid, whichis present in small amounts and which, when combined with the viscousfluid, interacts or reacts with the viscous fluid to form a product thatimpedes or prevents further mixing and/or the uniform interaction and/orreaction of the fluids. The mixer of the present invention, therefore,finds particular utility in the production of precheese and coagulantmixtures. Precheese is, at present, produced mostly by ultrafiltrationof milk to produce a viscous retentate (ultrafiltered milk). Theretentate, whose composition corresponds to the targeted cheese product,is thereafter mixed with a cheese-forming agent, a coagulant, such asrennet, to produce a cheese product.

The precheese which is mixed with coagulant to form the feed that istreated in accordance with the present invention is suitably formed byultrafiltration using ultrafiltration devices described in my copendingapplication, Ser. No. 08/694,125, now U.S. Pat. No. 5,817,235 filedsimultaneously herewith on the same day as the present application andentitled ANTI-TELESCOPING DEVICE FOR SPIRAL WOUND MEMBRANE MODULES, theteaching of which is incorporated herein by reference thereto.

The mixture of precheese and coagulant prepared using the mixing methodand mixing device of the present invention can be treated to form aribbon of cheese in accordance with the continuous cheese coagulationmethod described in my copending patent application, Ser. No.08/694,228, now U.S. Pat. No. 5,688,542 filed simultaneously herewith onthe same day as the present application and entitled CONTINUOUS CHEESECOAGULATION METHOD, the teaching of which is incorporated herein byreference thereto.

A critical step in the production of admixtures of coagulated precheeseis the mixing of rennet with the viscous milk retentate. Conventionalmixing devices often produce uneven mixing and, as a consequence,irregular coagulation occurs. Irregular coagulation produces layers inthe final cheese with poor, unacceptable structure. The viscosity of theretentate makes it difficult to evenly distribute the rennet,particularly because a very small amount of rennet is added to theretentate. The problem of irregular coagulation is exacerbated becauseretentate coagulates very rapidly in the presence of rennet. Theresulting coagulant (solid) makes it very difficult, if not impossible,to disperse the remaining rennet within the remaining liquid retentate.The mixer of the present invention specifically addresses this problem.The sequence of events involved in the mixing of retentate and rennet,in accordance with the present invention, is altered from theconventional sequence, dosing, followed by injecting, followed by mixing(dispersion or diffusion). In the present invention, a new sequence hasbeen adopted, namely, dosing, followed by "dispersion" of retentate(into a thin, annular film) followed by injection of rennet into the"dispersed" retentate.

In the prior art, mixing of rennet with retentate starts by dosing ormeasuring the relative amounts of the various components to be mixed.Then the retentate and rennet are introduced into a container for batchmixing or are kept flowing in a tube for continuous mixing. Variousdevices have been used to provide rotating or oscillating blades ofvarious shapes and forms, generally activated by an external source ofenergy, to promote the dispersion of rennet and retentate. Forcontinuous in-line mixing, the liquid mix flows inside a tube withstatic mixing elements therein.

In the embodiment of the present invention relating to formation ofprecheese, the method of the present invention involves (a) forming acontinuously flowing annular thin film of retentate; and (b) injectingretentate in predetermined small dosage levels into the thin film offlowing retentate. The angle of injection relative to the annularretentate film illustrated herein is radial to the axis of the annulusforming walls, however, any other angle relative to the surface ofretentate is acceptable.

Also, in accordance with the present invention, further mixing, inaddition to mixing caused by rennet injection into the moving retentatefilm, may occur downstream of the spray/injection apertures.

In accordance with the present invention, dispersion, after combinationof coagulant and precheese, is minimized by first dispersing retentate(into a thin annular film) before injecting rennet. In other words, theobjective of mixing in the present invention, is to "disperse" theprecheese and inject the coagulant so that first contact approximates asmuch as possible the architecture of a uniform dispersion of coagulantin retentate. Accordingly, the time consumed for combining componentsand the retention time after injection is minimized during the mixingcontinuum. The short duration of mixing, in accordance with the presentinvention, avoids partial coagulation. Accordingly, in the presentinvention, the components to be mixed are first divided into very small,easily-mixable portions. In the embodiment of the present inventionrelating to the production of precheese, this is done by creating acontinuously-flowing thin-film of retentate and a synchronized stream ofrennet. Referring to FIG. 1, retentate film fills and flows through theannular space between the mixer body 230 and the mixer head 250. Therennet stream is injected, circumferentially into the flowing thin-filmof retentate through a series of extremely fine nozzles formed at theinterface of the mixer head and mixer body optionally, further mixingand/or finishing may occur downstream of rennet injection and asspecifically shown in the illustrated embodiment of the mixer of thepresent invention, this can be achieved by frusto-conically shapedturbulence promoters placed downstream of the injection nozzles.

In the present invention, in order to minimize retention time within themixer, the retentate is passed through the mixer at a high linear speedwhich provides the additional benefit of reducing the actual viscosityof the retentate. Most preferably the physical size (internal volume) ofthe mixer is kept to the absolute minimum required. Also contemplated inaccordance with the present invention is the use of a finisher--anoptional element that can be installed to effect further mixing. Thefinisher reinforces the dispersion of rennet within the retentate andslows down the mix at the mixer outlet to avoid splashes in downstreamunit(s) where the coagulant and precheese mixture formed by the mixer iscoagulated and cheese is formed. The finisher of the present inventionillustrated in FIGS. 8 and 9 results in only minimal addition to theinternal volume of the mixer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an elevational view in section of the apparatus for mixingfluids.

FIG. 2 is an elevational view in section of the head adapter.

FIG. 3 is a bottom plan view of the head adapter illustrated in FIG. 2.

FIG. 4 is a partial view taken from FIG. 1.

FIG. 5 is a sectional view taken along lines 5--5 of FIG. 6.

FIG. 6 is an elevational view of the mixer head.

FIG. 7 is a sectional view taken along lines 7--7 of FIG. 6.

FIG. 8 is a sectional view illustrating the bores in the finisher.

FIG. 9 is a top plan view of FIG. 8.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring to FIG. 1, mixing assembly 200 is comprised of T-connector cap210, T-connector 220, mixer body 230, mixer head adaptor 240, and mixerhead 250. T-connector 220 is a simple, standard, sanitary 2-inch Teethat serves as inlet for retentate and as holder for mixer body 230 andT-connector cap 210. T-connector gasket 224 is used at the interfaces ofT-connector cap 210 and T-connector 220, T-connector 220 and mixer body230, and T-connector 220 and retentate inlet pipe 221 that are each heldtogether with a standard sanitary clamp 228.

As shown in FIGS. 1-3, mixer body 230, with mixer head 250 and mixerhead adapter 240 in place, forms a receiving chamber 232, an injection(mixer) chamber 234, and expansion chamber 236, also referred to herein,respectively, as the receiving/accelerating, injection and expansionzones and a turbulence chamber 239. Mixer head adapter 240 is centeredwithin T-connector 220 and attached to T-connector cap 210 with setscrew 212 in T-connector cap 210. Mixer head adapter 240 includes inletinternal threads 242 for coupling to piping from a rennet dosing pump,rennet conduit 244, adaptor centering lugs 246, accelerator 248, bottomsurface 247, injector grooves 245 and outlet internal threads 249.

Mixer head 250, as shown in FIGS. 1 and 5-7, has external threads 251,channels or open grooves 252, shoulder 253, retentate receiver 255,circular retentate receiver recess 256, frusto-conical turbulencepromoters 257, and centering lugs 258 for centering the mixer headwithin injection chamber 234.

When used in forming precheese where sanitary conditions have to bemaintained and frequent cleaning is required, the architecture of thismixing assembly facilitates disassembly and cleaning. The mixingassembly is suitably fabricated from stainless steel, for example 316L,although plastic as well as other metal alloys may also be used.

The retentate is introduced into T-connector 220 via T-connectorretentate inlet 222. Retentate then passes into mixer body 230 viaretentate passageway 226 into receiving chamber 232, which is alsoreferred to herein as the retentate acceleration zone, then entersinjection chamber 234 and next enters retentate turbulence zone 239.

In the illustrated embodiment of the invention as shown in FIGS. 1-9,rennet is introduced into head adaptor 240 through head adaptor inlet241. The dosage level of rennet required is calculated based on thevolume of retentate being processed. The required rennet is fed to headadaptor 240 from a suitable liquid dosing device. Dosing and devicescontrolling dosing of rennet and/or other precheese forming coagulantsare well known in the art and not a part of the present invention.Internal threads 242 are adapted to couple with a fitting which connectsto flexible tubing affixed to a rennet dosing device.

As best shown by reference to FIGS. 1 and 2, a portion of rennetinternal conduit 244 is delimited by the interior wall of the headadaptor bottom section which is internally threaded to engage externalthreads 251 of mixer head 250.

The exterior surface of these threads 251 and of shoulder 253 of mixerhead 250 is provided with four equally spaced grooves 252 which arelongitudinally disposed, as best shown in FIGS. 5, 6, and 7. When mixerhead 250 is engaged with mixer head adapter 240, bottom surface 247abuts mixer head engaging surface 259, as best shown in FIGS. 1 and 4. Adistribution manifold for the rennet passing through grooves 252 isformed by circular receiver 256 and the overlying portion of the bottomsurface 247 of mixer head adapter 240.

The grooving on bottom surface 247 of head adapter 240 is best shown inFIGS. 2, 3 and 4. The radial grooves 245, as shown, extend radiallyoutward from the axis of head adaptor 240, preferably terminatingequidistant one from the other and forming circumferentially disposedinjection apertures/ports, whereby the rennet is injected into theretentate flowing through the annulus formed by the interior wall ofmixer body 230 and the exterior surfaces of mixer head 250 and mixerhead adapter 240.

The surfaces of mixer head adapter 240 and the mixer head 250 in nearproximity to mixer body 230 delimit three contiguous zones. The first isretentate accelerating zone 232 where the retentate is accelerated andformed into a thin film. Downstream of accelerating zone 232 isinjection zone 234 where the rennet is continuously sprayed into theretentate, preferably substantially normal to the direction/vector offilm flow and also preferably from ejection ports evenly distributed,formed by radial rennet grooves 245. Downstream of injection zone 234 isturbulence 239 which may be used to advantage to effect additionalmixture.

Alternative architecture for the mixer, in accordance with the presentinvention, includes injection through the exterior wall forming theannular thin film stream, suitably through injection ports that arecircumferentially spaced apart or in other arrays and patterns toprovide for alternative/supplemental introduction of rennet throughmixer body 230. Injection vectors in an upstream direction or evendownstream direction may be used. Injection, as illustrated, is as mucha consequence of mixer architecture for forming the injection portsusing the assembly of mixer and mixer adapter as by design to provideinjection in a direction substantially normal to the plane of flow.Accordingly, injection ports/apertures can be opposed, facing oneanother with injection from the exterior and interior walls forming theannulus or offset with criss-cross injection and the like. Since theobjective is uniform mixture, the array of injection ports is preferablycircumferential. Moreover, In the illustrative embodiment of the presentinvention, the obvious alternative for forming the rennet injectionports is to form radial grooves on surface 259 as opposed to or even inaddition to surface 247. The concentric walls forming the annulus, aswill be appreciated, are not limited to circular form, other shapesbeing acceptable and/or convergence or divergence being contemplated,provided only that the dispersion of the annularly flowing fluid is notsubstantially diminished whereby uniformity of admixture is adverselyaffected.

The mixer of the present invention may advantageously include aturbulence zone 239 wherein the mixed retentate and rennet are subjectedto turbulence while passing over eight turbulence promoters 257, which,as shown, are frusto-conical with gradually decreasing wall diameter inthe downstream direction. The admixture of rennet and retentate flowspast lugs 258 into expansion chamber 236, having conical surface 259,for final discharge from mixer body 230.

In the embodiment of the invention illustrated in FIGS. 8 and 9, thedischarge end of the mixing assembly is adapted for use with what isreferred to herein as a finisher that may be used when mixing extremelydifficult components. The function of the finisher is to secure an evenmix for extremely difficult components by forcing the mix exiting themixer body to pass through a series of orifices that reverse positionand sense of rotation of the liquid layer. After that, there is a finalexpansion chamber to slow down the liquid mix before reaching the outletport in the finisher cap.

The bottom of mixer body 230 is configured to accommodate conical top262 of finisher 260 and in combination therewith to form mixerdistribution zone 264. Circumscribing conical top 262 is planar annularsurface 261 which has a series of cross-oriented, paired finisherconduits 266 that serve to reverse position and to rotate mixture beingfinished. The finished mix is discharged into cylindrical channel 268.

As shown in FIG. 8, finisher 260 is attached to mixer body 230 by agasket 263 and a standard clamp (not shown in drawings), and finishercap 270 is also attached by means of a gasket 263 and a standard clampunion (also not shown) to finisher 260. Finisher cap 270, in conjunctionwith finisher 260, forms finishing zone 272 and provides precheeseoutlet 274.

The size of the mixer may vary dependant on the size and nature ofcheese being formed. It is contemplated in accordance with the presentinvention to combine a plurality of small mixing assemblies and toconsolidate their effluent into a single stream.

As an example, where a typical two-inch T-section was used forfabrication of the mixer assembly, the mixer head was constructed of0.375" diameter stainless steel. The opposing walls which delimit thefilm thickness were situated about 1.5 to 2 mm apart to form a retentatefilm of corresponding thickness. In such assembly the spaced-apartrennet grooves suitably are 20-30 in number (they are located 12-18degrees apart) and about 0.003 inches deep and V-shaped.

The mixing assembly of the present invention is particularly adapted toproviding a highly uniform admixture of coagulant and precheese in acontinuous stream which can be formed into a continuous rope of cheeseproduct. This continuous rope of cheese can be cut into cheese portionsof any desired weight. The advantages of uniform mixture achieved in thepresent mixer also find applications in non-continuous operations. Theachievement of uniform admixture using the mixer assembly of the presentinvention, including the optional finisher, also further findsapplication with other feedstocks in addition to rennet and retentate.

The method finds general application in mixing a variety of fluids,especially fluids comprised of liquids which in the absence of rapiduniform admixture tend to coagulate/solidify in a non-uniform manner andform multiphase/polyphase admixtures and/or otherwise non-uniformproducts. The apparatus and method of this invention can accordingly beused in all applications where rapid uniform mixing is advantageous.This includes production of physical mixtures without interaction,production of reactant mixtures, including polymerization and catalyticprocesses.

Moreover, the mixing method of the present invention and the describedmixer may be sized appropriate to the materials being treated and infact mixing can be effected using a plurality of mixers in series or inparallel. In series, the mixing is sequential and the components thatare added in each succeeding mixer may differ.

In the case of formation of a coagulant and precheese mixture, where themass of mixture required is a multiple of the precheese exiting a singlemixer, the admixtures of parallel mixers may be combined.

The mixing assembly of the present invention finds particular utility inthe critical step of cheese production by ultrafiltration of milk,because such process involves the mixing of rennet with highly viscousmilk retentate. The use of conventional mixing devices often producesuneven mixing and, as a consequence, irregular coagulation is obtained.Irregular coagulation produces layers in the final cheese with poor,unacceptable structure.

This problem occurs because the high viscosity of the retentate makes itdifficult to distribute the dosed rennet evenly. (Rennet is added invery small amounts compared with the retentate into which the rennet isadded.) An added difficulty derives from the fact that retentate reactsvery rapidly with rennet so that the mixture simultaneously coagulates,becoming solid and therefore making it very difficult, if notimpossible, to disperse the remaining rennet within the remainingretentate in liquid form. The mixing assembly of the present inventionaddresses this problem and enables continuous precheese formation tooccur.

In accordance with the present invention the conventional sequence(dosing, followed by injecting, followed by dispersion or diffusion) ischanged to a new sequence (dosing, followed by dispersion, followed byinjecting). In addition, the mixing assembly and method of theembodiment of the present invention relating to mixing, treats retentatewhich is moving at very high linear speed inside the mixer--with theadditional benefit of reducing the actual viscosity of the retentate.The physical size (internal volume) of the mixer can be kept to theabsolute minimum required.

The linear flow is adjusted to avoid even partial coagulation. The timethat the retentate spends in the mixing device following injection untilit exits is most preferably on the order of hundredths of a second and,in any event, less than half a second. The thickness of the retentatefilm in the annulus is most preferably in the range of from about 1.5 mmto about 2 mm although films of from about 0.5 mm to about 3 mm, can beused, although not necessarily with the same results.

Referring to the embodiment of the invention illustrated in thedrawings, the mixer head is most preferably on the order of 3 inches inlength, and preferably less than 6 inches in length. Depending on thetarget capacity, the diameter of the annulus is adjusted to increase ordecrease capacity. This is done by changing the diameter of the mixinghead with, of course, a corresponding change in the mixer body tomaintain the selected thickness of the film.

The finisher--an optional part that can be installed ifneeded--reinforces the dispersion of rennet within the retentate andslows down the mix to avoid splashes in the coagulation unit to whichthe precheese admixture made in accordance with the present invention isfed. In accordance with the present invention, addition to the internalvolume of the mixer is minimal.

The mixer body is machined from a solid piece of material (eitherstainless steel or sanitary polymer) with a clamp union on each end toattach it to the T-connector at its upper end and to the finisher on thelower end.

The mixer body can be viewed as having three chambers:

a. a receiving chamber for retentate. In this part the formation of athin layer of retentate is initiated in preparation for the rennetinjection.

b. an injection chamber, where the rennet is actually injected into thethin layer of retentate created in the receiving chamber. Afterinjection of rennet, the thin layer mix optionally encounters a seriesof turbulence promoters (eight are shown) to facilitate evendistribution of rennet.

c. an expansion chamber, where the thin layer of retentate-rennet mixslows down and exits the mixer body and optionally enters a finisher.

The use of a head adaptor allows the use of the same mixer withdifferent heads and bodies. It provides the connection of the mixer headto the T-connector cap, centers the mixer head in relation to the mixerbody and serves as a conduit for the rennet between the rennet inletport at the T-connector cap and the rennet nozzles at the upper part ofthe mixer head.

The mixer head is a critical part of the mixer assembly. Together withthe mixer body, it forms the thin layer of retentate essential for agood, even mix. The upper part of the mixer head contains threads toattach it firmly to the head adapter. Alignment with the head adapter issecured by a shoulder that follows the threaded part. Threads andshoulder have open channels cut across them to allow the rennet to reachthe nozzles. The mid part of the mixer head contains the injectionnozzles to evenly distribute the rennet full circle. The lower part ofthe mixer head has turbulence promoters cut into it.

The finisher is an optional part. Its function is to secure an even mixin those cases of extremely difficult products by forcing the mixexiting the mixer body to pass through a series of orifices that reverseposition and sense of rotation of the liquid layer. After that, there isa final expansion chamber to slow down the liquid mix before reachingthe outlet port in the finisher cap.

Attached to the finisher by means of standard clamp union, the finishercap provides the outlet port for the liquid mix. It can be fitted withan internal mesh (not shown) to further reduce splashing.

It is not intended to limit the method and/or apparatus of the presentinvention to the particular embodiment described herein, and variousmodifications may be made, including, but not limited to, changes indimensions, shape and materials, without departing from the scope andspirit of the invention as set forth in the following claims.

I claim:
 1. A device having a plurality of circumferentially spaced injection ports, which comprises:(a) a first cylinder having an inlet end, an outlet end, an axial opening extending from said inlet end to said outlet end and a bottom surface; (b) a second cylinder having an upper end and a lower end, said upper end having an upper end surface; (c) means for affixing said first and second cylinder together with said bottom surface of the first cylinder extending from said upper end surface of said second cylinder; (d) means for providing said circumferentially spaced injection ports at an interface where said bottom surface of said first cylinder abuts the upper end surface of said second cylinder; and (e) means for providing a passageway from said inlet end of the first cylinder to said circumferentially spaced injection ports.
 2. The device of claims 1, wherein the means for affixing said first and second cylinders together is comprised of internal threads within the axial opening of said first cylinder and a third cylinder extending axially up from a central portion of the upper end surface of said second cylinder into the axial opening of said first cylinder having external threads, the external threads of said third cylinder engaging the internal threads within the axial opening of said first cylinder.
 3. The device of claim 2, wherein the means for providing a passageway from said inlet end of the first cylinder to said circumferentially spaced injection ports comprises:(i) one or more openings extending the length of the interface between said first and third cylinders; (ii) a circular manifold at the interface between said first and second cylinders in open communication with said one or more openings extending the length of the interface between said first and third cylinders; and (iii) radial grooves on the bottom surface of the first cylinder or upper end surface of the second surface which form openings interconnecting said circumferentially spaced injection ports to said circular manifold.
 4. The device of claim 1, wherein the second cylinder further comprises a turbulence creating means intermediate the upper and lower ends thereof.
 5. The device of claim 4, wherein said turbulence creating means comprises a plurality of frusto-conical elements arranged in series.
 6. The device of claim 1, where the means for providing said circumferentially spaced injection ports at an interface where said bottom surface of said first cylinder abuts the upper end surface of said second cylinder comprises radial grooves on the bottom surface of said first cylinder.
 7. The device of claim 1, where the means for providing said circumferentially spaced injection ports at an interface where said bottom surface of said first cylinder abuts the upper end surface of said second cylinder comprises radial grooves on the upper end surface of said second cylinder.
 8. A mixer comprising:(a) means for forming an annulus having an inlet and outlet; (b) means for introducing a first fluid into said annulus inlet; (c) means for introducing a second fluid into said annulus intermediate the inlet and outlet of the annulus; said means for introducing said second fluid into said annulus having a plurality of circumferentially spaced injection ports and comprising:(a) a first cylinder having an inlet end, an outlet end, an axial opening extending from said inlet end to said outlet end and a bottom surface; (b) a second cylinder having an upper end and a lower end, said upper end having an upper end surface; (c) means for affixing said first and second cylinder together with said bottom surface of the first cylinder abutting said upper end surface of said second cylinder; (d) means for providing said circumferentially spaced injection ports at an interface where said bottom surface of said first cylinder abuts the upper end surface of said second cylinder; and (e) means for providing an open passageway from said inlet end of the first cylinder to said circumferentially spaced injection ports.
 9. The mixer of claim 8, wherein the means for affixing said first and second cylinders together is comprised of internal threads within the axial opening of said first cylinder and a third cylinder extending axially up from a central portion of the upper end surface of said second cylinder into the axial opening of said first cylinder having external threads, the external threads of said third cylinder engaging the internal threads within the axial opening of said first cylinder.
 10. The mixer of claim 9, wherein the means for providing a passageway from said inlet end of the first cylinder to said circumferentially spaced injection ports comprises:(i) one or more openings extending the length of the interface between said first and third cylinders; (ii) a circular manifold at the interface between said first and second cylinders in open communication with said one or more openings extending the length of the interface between said first and third cylinders; and (iii) radial grooves on the bottom surface of the first cylinder or upper end surface of the second surface which form openings interconnecting said circumferentially spaced injection ports to said circular manifold.
 11. The mixer of claim 8, wherein the second cylinder further comprises a turbulence creating means intermediate the upper and lower ends thereof.
 12. The mixer of claim 9, wherein the second cylinder further comprises a turbulence creating means intermediate the upper and lower ends thereof.
 13. The mixer of claim 10, wherein the second cylinder further comprises a turbulence creating means intermediate the upper and lower ends thereof. 